Reactor unloading means



ug- 20 1957 c. M. COOPER 2,803,601

REAcToR uNLoADING MEANS 3 Shee'ts-Sheei 1 Filed Oct. 16. 1945 fazesses.-

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. Aug. 20, 1957 c. M. COOPER REACTOR UNLOADING MEANS 3 Sheets-Sheet 2 Filed Oct. 16, 1945 giiili Aug 20, 1957 c. M. COOPER 2,803,601

REACTOR UNLOADING MEANS Filed OCT.. 16, 1945 5 Sheets-Sheet 5 /Z 9 F1154. fj /0 @292655 e5.' fila/272 Zof f United States Patent() M UNLOADING MEANS Charles M. Cooper, Newark, Del., assigner to the United States of America as represented by the United States Atomic Energy Commission The present invention relates generally to a means and method of safely handling radioactive material, and particularly to a means and method of transporting highly radioactive material, such asv uranium, after it has been irradiated with neutrons in high density, such as exists in neutronic reactors.

It is known that a self-sustaining chain reaction can be obtained in devices known as neutronic reactors utili`zing natural uranium as a result of slow neutron ssion of the U235 content of the natural uranium and that such self-sustaining chain reaction may be used to produce power, as has been fully described and claimed in the Fermi and Szilard application, Serial Number 568,904,

led December 19, 1944, now Patent No. 2,708,656, dated' May 17, 1955. In such reactors, discrete bodies of natural uranium of high purity are disposed, usually inthe form of a lattice arrangement of spheres or rods, in a neutron moderator such `as graphite, beryllium or heavy water of high purity, surrounded by a neutron reector. Neutron absorption in the U238 content of the natural uranium during the reaction leads to the production of the transuranic isotope 94239 of element 94, known as plutonium (symbol Pu), which isotope is fissionable in much the same manner as U235. 94239 is formed in neutronic reactors utilizing natural uranium in accordance with the following process: v

94239 in high purity and concentration is recoverable from the-uranium in the reactors after operation by chemical processes. In neutronic reactors operating at elevated powers such as, for example, 5,000 to 250,000 kilowatts, a large amount of heat is generated in the uranium bodies. Therefore the uranium bodies in the reactor are cooled by passage of a coolant in heat eX- change relation therewith. Furthermore, in order to recover the 94239 produced in the reactor the uranium is customarily removed atintervals for chemical processing. Fission of the U23? existing in the uranium bodies creates large quantities of fission products, defined as including original fission fragments and their daughter decay products. The end result is that the uranium bodies become so `radioactive after long irradiation `that they cannot be handled for many days-without adequate personnel shielding, depending on the time and density of irradiation.

long after the irradiation has ceased.

2,803,601 Patented Aug. 20, 1957` ICC These latter requirements complicate the discharge of uranium bodies from neutronic reactors, and it is an object of the present invention to provide a means and method of transporting highly radioactive bodies, such as uranium bodies irradiated with neutrons in a neutronic reactor, from the reactor, preferably quickly after shutdown, to a remote location where the bodies can safely age until the radioactivity is reduced and the reactor can be quickly reloaded with fresh material, thus shortening materially the shutdown period of the reactor.

It is another object of the present invention to supply adequate cooling for the uranium bodies at all times during transport' from the reactor to the aging location.

'The present invention will be described as used in conjunction with a neutronic reactor wherein uranium bodies in the form of short cylindrical slugs are disposed in rod geometry in coolant tubes running vthrough the reactor. The details of such a reactor are disclosed and claimed in the co-pending application above cited. For this reason the neutronic reactor will only be diagrammatically represented in the drawings appended hereto, as follows:

Fig. 1 is a diagrammatic elevational view, partly in section, of a water cooled neutronic reaction embodyingV the present invention;

Fig. 2 is a transverse cross sectional View of a typical coolant tube with a uranium slug therein;

Fig. 3 is a fragmentary enlarged diagrammatic elevational view, partly in section, showing a slug transport and cooling system embodying the present invention;

Fig. 4 is a longitudinal sectional view of-a uranium slug to be transported;

Fig. 5 is a vertical sectional view of a slug handling valve, as indicated by the line 5-5 shown in Figure 6; and

Fig. 6 is a horizontal sectional view taken as indicated by the line 6-6 in Fig. 5.

Referring rst to Fig. l showing the gross assembly of a neutronic reactor embodying the present invention, the neutronic reactor system comprises a mass or block of neutron moderator such as graphite of substantially cubical shape, indicated by the dotted line 1. The moderator block 1 is closely surrounded on all but one side by a radiation shield 2 of concrete, for example, 5 to 10 feet thick. The remaining side has a radiation shielding wall 4 spaced from the open face 5 of the moderator block. A plurality of coolant tubes 6 extend in parallel relationship through the reactor from a. charging face 7 outside of the shield 2 to the open face 5 inside wall 4.

The coolant tubes 6 are shown in more detail in Figs. 2 and 3. The tubes 6 are inserted in the graphite moderator and have a number of internal ridges S supporting and spacing from the tube walls a plurality of uranium bodies 9 covered with a sealed aluminum jacket 10 to prevent the coolant flowing in annulus 11 from corroding the uranium bodies 9. A single jacketed uranium body is customarily called a slug and the slugs are insertedin end to end relationship Vin the tubes to eifectively form rods extending through the moderator block 1. In a typical neutronic reactor of this type, the slugs are 1.1 inches in diameter and 4 inches long.

One way in which the slugs are sealed is shown in Fig. 4. The jacket 10 is either forced over or bonded to the uranium body 9 with the open end projecting. A cup-shaped cap 12 is placed over the exposed end of the body 9 and the registering edges of jacket and cup welded movable on tracks along the charging face 7 so that any tube can be charged with slugs.

Charging ends 17 of they tubes 6 extend through the chargingyface 7, which, .afterthe .tube is charged with slugs, are provided with caps .18 .as ,shown inV Fig. 3.

Water is .supplied throug'h .inletv19'in each tube 6; Vthe water 'passes through the tubes-6 and over Vthe slugs to cooltheiti. p y Y p 'ft the 'u'tletcn'd's 42,0 .of the tubes l6, a special slug valveA 2,1 is providemnormall'y Vclosing the outlet end of ea'c'h tube, anda water outlet 22 .is providedtor each tube between vwl'v'e 2.1 andthe moderator block. Coolantinlets 19 and tlet's A2'2 are connected'to'manifolds (not shown), and water is circulated vunder vpressurewthrough 'the tubes xli'ring operation of the reactor.

After operafiomfQr example, for '50 days at 1005000 lilowatts, Iitrnaybe desirable to discharge fall or part of the uranium in order that t-he 94239 formed can ,be recovered. However, the radioactivity of the slugs is very high, .so high infact that cooling cannot bc entirely discontinued 'because of the self-heating of the uranium slugs du'e to the absorption or" their own radioactivity. YThe present .invention provides a means and method of simultaneously cooling and transporting the irradiated slugs to a remote location where they can safely age prior to chemicaltreatment. Due to the fact that the-slugs are both cooled and shielded during transport, thereactor Y can be unloaded substantially immediately after shutdown of the chain reaction.

The reactor is first shut down and the lapse of a few minutes is allowed for the emission of delayed neutrons from the tissions. Water circulation'through tubes 6 can lEhen bev reduced Yto k10 or 25 percent of its full operating.

value, 'according to the power existing before shutdown. One tube 6 is th'en opened at the charging face 7 by removal of cap 18. Water circulation is continued in the open tube,` some of the water spilling out of the open end of lthe tube' 6 until plunger V15 is inserted. This plunger `does not have to prevent all water leakage at the open endk of the tube, but merely serves to block the *open end .suiciently to cause water to continue flowing through the tube 6 to the discharge end.

` Slug valve 2.1fis constructed tovreceive a single slug, as shown in Figs.` and 6. A valve casing 23v is provided in which the discharge end 20 of a tube 6 terminates. Inside the casing is .a lrotatable plug 24 havinga slug recess 245 therein into which a single slug can be pushed by plunger pressure on the opposite end of the string of slugs. Thefplug24i's then turned 90 by a remotely operated n handle 26 yto drop the-slug by Ygravity into a hydraulic conveying tube "27 entering thecasing as shown in Figs. 3 and 45. Y v ,K p

,Y As soon as the slug,V enters conveying tubek 27, water underpressure is placed behind the slug from 'pump 30 under .control of pressure v alve 31 through tubef`32 passing through shielding wall 4. This water pressure pushes thefslugthrough the tube 27 to discharge the slug along with the water into a remote aging tankV 35.V Tube 27 is provided with lead or concrete shielding 36,- forex-x ample, andcan -be up to 500 feet long without.excessive A pumping pressures being required. In this manner, all

of the'slugs in any tube 4in the reactor can ybe conveyed` to the aging tank 35 shortly after shutdown and without the necessity of approach'by any operating personnel.

The emptied tube 6 can then be reloaded with fresh slugs as desired. .Theunloadinghof other tubes 6 can then be accomplished afsdesired, in the Vsame manner.

vv"alslug transportsystemAof-the type described,rl00 "Y "feet long, 71.38 I. D.se'amless steel tubing has been used li'quiclggunde'r pressure tolfaA body linfsaid clonveyr tube--` away from said valve forrdischargeat 'a remote locatng f Pressure Water Slug Drop Velocity Velocity (Average) (Ft./sec.) (Ft./sec.) (Lb./

. Y. V Sq.in.)

8.6 '6.8l 1 "81 11.1 7 3 "12.5 l 14.8 .10.4 18.5 ',17.6 l12.6 1 23.0 21.0 r115.7 g Y 32.5 24.4 18,2 41:0

A minimum Water velocity of 81fee`t per second was required for conveying one slug.

It will be noted from the above that the water velocity is consistently greater` than the slugvelocity. This leakage 'arouudthe slug is deliberately introduced, in that vit provides ,a water flowfaro'und the slug suicient to cool it while being transported, without possibility of boiling taking place in the conveying fluid, thereby eliminating vapor lock. Y v

On arrival at the aging tank 35, the slugs are discharged into water, and boiling in that tanl prevents :slug ktem per'aturesfrom rising over I100 C. If boiling is excessive, cool water can be circulated through Vtheftank.

The system as described is fully operableto transport radioactive slugs 500 feet or more vas desired, with coir'il plete land effective cooling while en route. 3

l several points should be noted. The slugvawe 'zii in 'reactors 'having -a large Vnumber of tubes, a single slug valve ycan be used and applied to the dischargek ends .of theA tube to be unloaded, with the first portion 'of the 'conveyor tube and the water supply tube being exible to permit the use of the same slug valve on a number of tubes. In either case, however, the action of the system is identical.

While the present invention has been described asparticularly useful in transporting radioactive bodies 'from a neutronic reactor to `an aging tank, it is equally -use'ful in transporting materials made radioactive in any maririer,V as, for example, by irradiation with particles accelerated in a cyclotron or similar device. Y

What is claimed is: Y v

. In combinationya neutronic reactor having Ta c'o'ol'ant tube extending therethrough, uranium lcontainingbodi'e's in4 saidvgtube lsized .to .provide a coolant 'channelitl-Iere-V aroundj-acoolant;inlet and outlet 'at respectige. ends'fo'f tube and .having a member provided fwith-arecess v'to .re-V

ceiveauranium'containing body when in one position,`'

said member being-rotatableto drop Aa received body under the inuence oflgravity, 'a meansfor `.pushing a body said body beingfa loose t in saidconveyor tube to proa 6 vide a substantial liquid ow around said body during 2,229,610 Nicholoy Ian. 21, 1941 passage along said conveyor tube. 2,396,305 TOft Mar. 12, 1946 2,708,656 Fermi et a1 May 17, 1955 References Cited 1n the file of this patent FOREIGN PATENTS UNITED STATES PATENTS 114,150 Australia May 2, 1940 alswn Mv'tozJ 233,011 switzerland ocaz, 1944 ayne c 2,078,235 Chapman Apr. 27, 1937 OTHER REFERENCES 2,087,391 Toulmin July 20, 1937 10 Smyth: Atomic Energy for Military Purposes, pages 2,127,193 Toulmin Aug. 16, 1938 103, 104, August 1945. Copy may be purchased from 2,165,397 Mason et a1. July 11, 1939 Supt. of Documents, Washington 25, D. C. 

